In the related art, Patent Document 1 discloses a flush toilet that has been proposed as a device in which cleaning water is prevented from overflowing due to filth or the like clogged in a trap pipeline of a toilet bowl. In this flush toilet, an inflow port for a relief flow channel extending in a horizontal direction is installed in the vicinity of an upper end of a bowl portion connected to the trap pipeline, and a drain flow channel leading to another water pipe from an outflow port on the other end side thereof is connected. A water level sensing sensor is provided at a position lower than the outflow port inside the relief flow channel.
In a case where a water level of cleaning water supplied to the bowl portion rises due to clogging or the like of the trap pipeline, the water level sensing sensor senses the cleaning water flowing into the relief flow channel in the vicinity of the upper end of the bowl portion, and the cleaning water stops being supplied to the bowl portion. The water level sensing sensor prevents overflowing of water supplied to the inside of the bowl portion, that is, overflowing of water from the bowl portion.
Patent Document 1 Japanese Unexamined Patent Application, First Publication No. 2011-140833.